Equalizing reference surface capacitance with uneven thickness

ABSTRACT

One embodiment in accordance with the invention includes a capacitive sensing apparatus that includes a capacitive sensor configured to sense an object proximate to a physical capacitive sensing reference surface. The capacitive sensing apparatus also includes a plurality of dielectric materials disposed between the capacitive sensor and the physical capacitive sensing reference surface. Note that at least one of the plurality of dielectric materials has a non-uniform thickness. The plurality of dielectric materials can be configured such that capacitive coupling between the capacitive sensor and the object proximate to the physical capacitive sensing reference surface is substantially constant across the physical capacitive sensing reference surface.

BACKGROUND

Conventional computing devices provide several input options forenabling a user to control such a computing device. For example, a usercan use one or more physical keys of an alphanumeric keyboardcommunicatively connected to the computing device in order to controlthe computing device. Additionally, a user can use a movable cursorcontrol device such as a mouse, a trackball, or a joystickcommunicatively connected to the computing device. Moreover, touchsensing technology can be used to provide an input option for usercontrol of a computing device or other electronic device. The user mayuse the input device to indicate desired actions in menu navigation,cursor control, game play, and inputting a choice or a selection.

Within the broad category of touch sensing technology there existcapacitive sensing touchpad devices. Typically capacitive sensingtouchpad devices are implemented with an input region in a flat orplanar manner as shown in FIG. 1. FIG. 1 is a side sectional view of anexemplary conventional art design of a capacitive sensing touchpad 100wherein a capacitive sensor 104 (which is well known in the art) cansense through a flat dielectric material 102. However, it can bedesirable to produce a capacitive sensing touchpad device in the shapeof a concave bowl, convex surface, or other non-flat shape. For example,the non-flat shape may be designed for industrial design reasons such asaesthetic appeal, or for functional reasons such as to ergonomically fitand to accompany the range of motion of a user's finger or thumb. One ofthe disadvantages of producing such a non-flat shaped capacitive sensingtouchpad device is that it can result in non-uniform signal output dueto non-uniform capacitive coupling, or be costly to design andfabricate.

The invention may address one or more of the above-identified issues.

SUMMARY

One embodiment in accordance with the invention includes a capacitivesensing apparatus that includes a capacitive sensor configured to sensean object proximate to a physical capacitive sensing reference surface.The capacitive sensing apparatus also includes a plurality of dielectricmaterials disposed between the capacitive sensor and the physicalcapacitive sensing reference surface. Note that at least one of theplurality of dielectric materials has a non-uniform thickness. Theplurality of dielectric materials can be configured such that capacitivecoupling between the capacitive sensor and the object proximate to thephysical capacitive sensing reference surface is substantially constantacross the physical capacitive sensing reference surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of an exemplary conventional art designof a capacitive sensing touchpad.

FIG. 2 is a plan view of an exemplary capacitive sensor apparatus thatcan be implemented to include one or more embodiments in accordance withthe invention.

FIG. 3 is a top view of an exemplary capacitive sensing apparatus inaccordance with various embodiments of the invention.

FIG. 4 is an exemplary side sectional view of a capacitive sensingapparatus of FIG. 3.

FIG. 5 is an exemplary side sectional view of another capacitive sensingapparatus of FIG. 3.

FIG. 6 is an exemplary side sectional view of a capacitive sensingapparatus of FIG. 3 in accordance with various embodiments of theinvention.

FIG. 7 is another exemplary side sectional view of the capacitivesensing apparatus of FIG. 3 in accordance with various embodiments ofthe invention.

FIG. 8 is yet another exemplary side sectional view of capacitivesensing apparatus of FIG. 3 in accordance with various embodiments ofthe invention.

FIG. 9 is still another exemplary side sectional view of capacitivesensing apparatus of FIG. 3 in accordance with various embodiments ofthe invention.

FIG. 10 is another exemplary side sectional view of capacitive sensingapparatus of FIG. 3 in accordance with various embodiments of theinvention.

FIG. 11 is a top view of another exemplary capacitive sensing apparatusin accordance with various embodiments of the invention.

FIG. 12 is an exemplary side sectional view of the capacitive sensingapparatus of FIG. 11 in accordance with various embodiments of theinvention.

FIG. 13 is a flow diagram of a method in accordance with variousembodiments of the invention for forming a capacitive sensor apparatus.

FIG. 14 is a top view of another exemplary capacitive sensing apparatusin accordance with various embodiments of the invention.

FIG. 15 is an exemplary side sectional view of the capacitive sensingapparatus of FIG. 14 in accordance with various embodiments of theinvention.

FIG. 16 is a top view of yet another exemplary capacitive sensingapparatus in accordance with various embodiments of the invention.

FIG. 17 is an exemplary side sectional view of the capacitive sensingapparatus of FIG. 16 in accordance with various embodiments of theinvention.

The drawings referred to in the detailed description should not beunderstood as being drawn to scale unless specifically noted.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments inaccordance with the invention, examples of which are illustrated in theaccompanying drawings. While the invention will be described inconjunction with various embodiments, it will be understood that thesevarious embodiments are not intended to limit the invention. On thecontrary, the invention is intended to cover alternatives, modificationsand equivalents, which may be included within the scope of the inventionas construed according to the Claims. Furthermore, in the followingdetailed description of various embodiments in accordance with theinvention, numerous specific details are set forth in order to provide athorough understanding of the invention. However, it will be evident toone of ordinary skill in the art that the invention may be practicedwithout these specific details. In other instances, well known methods,procedures, components, and circuits have not been described in detailas not to unnecessarily obscure aspects of the invention.

FIG. 2 is a plan view of an exemplary capacitive sensor 200 that can beimplemented to include one or more embodiments in accordance with theinvention. The capacitive sensor 200 can be utilized to communicate userinput (e.g., using a user's finger, a probe, a stylus, or an object) toa computing device or other electronic device. For example, capacitivesensor 200 can be implemented as a capacitive touchpad device that canbe disposed in or on a computing device or other electronic device toenable user interfacing with the computing or electronic device. Notethat one or more embodiments in accordance with the invention can beincorporated with a capacitive touchpad device similar to capacitivesensor 200.

The capacitive sensor 200 when implemented as a touchpad can include asubstrate 202 having a first set of conductive traces 204 and optionallya second set of conductive traces 206 patterned (or formed) thereon.Substrate 202 of capacitive sensor 200 can be implemented with, but isnot limited to, one or more insulating materials that are utilized as asubstrate for a capacitive touchpad device. The combination of the setsof conductive traces 204 and 206 defines a sensing region 208 ofcapacitive sensor 200. Note that the sensing pattern shown withinsensing region 208 is exemplary. As such, sensing region 208 can includeany type of sensing pattern formed by the set of conductive traces 204and the set of conductive traces 206. The sets of conductive traces 204and 206 can be coupled to sensing circuitry 210, thereby enabling theoperation of capacitive sensor 200. Although FIG. 2 shows two sets ofconductive coupling traces 204 and 206, each including multipleconductive traces, the capacitive sensor 200 may be implemented withonly one set of conductive traces, and/or only one conductive trace orelement per set. It is also noted that the exemplary sensing elementpattern shown within sensing region 208 is one of any number of sensingelement pattern that can be implemented in accordance with variousembodiments of the invention. For example, the capacitive sensor 200 canbe implemented as a matrix of intersecting electrodes (such as the oneshown) or alternate patterns with or without intersecting electrodes.Although the capacitive sensor 200 is also shown having a rectilinearcharacteristic, it is not limited to such, and can be implemented havinga round or ring-like characteristic, or any other shape having anynumber of straight or curved aspects. The capacitive sensor 200 can alsobe implemented as a two-dimensional capacitive sensor (such as the oneshown), or as a one-dimensional capacitive sensor (not shown), but isnot limited to such.

FIG. 3 is a top view of an exemplary capacitive sensing apparatus 300that includes a concave bowl shaped physical (i.e. tangible) capacitivesensing reference surface 302 in accordance with various embodiments ofthe invention. Additionally, FIG. 4 is a side sectional view fromviewpoint A-A of the capacitive sensing apparatus 300. Within FIGS. 3and 4, the capacitive sensing apparatus 300 includes a capacitive sensor200 configured to sense object 303 (e.g., a user's finger, a probe, astylus, and the like) proximate to the physical capacitive sensingreference surface 302.

The capacitive sensing reference surface 302 can be the upper surface ofa dielectric material 402, which has non-uniform thickness. It is notedthat the capacitive coupling (or specific capacitance per unit area)between the capacitive sensor 200 and an object (e.g., finger 303)proximate to the physical capacitive sensing reference surface 302 isnon-uniform as object 303 moves across the physical capacitive sensingreference surface 302. One way to compensate for the non-uniformcapacitive coupling signal output by capacitive sensor 300 is to utilizecircuitry and/or software that can be associated with sensing circuitry210.

FIG. 5 is a side sectional view from viewpoint A-A of an exemplarycapacitive sensing apparatus 300A that includes a concave bowl shapedphysical (i.e. tangible) capacitive sensing reference surface 302. Thecapacitive sensing apparatus 400 includes capacitive sensor 200configured to sense an object (e.g., a user's finger, a probe, a stylus,and the like) 303 proximate to the physical capacitive sensing referencesurface 302. The capacitive sensing reference surface 302 can be theupper surface of the dielectric material 402, which has a substantiallyuniform thickness. Furthermore, the capacitive sensor 200 has beenimplemented in a concave shape that substantially follows the concaveshape of capacitive sensing reference surface 302. It is understood thatthe capacitive coupling (or specific capacitance per unit area) betweenthe capacitive sensor 200 and an object (e.g., finger 303) proximate tothe physical capacitive sensing reference surface 302 is substantiallyuniform as object 303 moves across the physical capacitive sensingreference surface 302. As such, typical sensing circuit 210 can beutilized in conjunction with capacitive sensing apparatus 400. However,one drawback associated with the capacitive sensing apparatus 400 isthat it may be costly to manufacture.

FIG. 6 is a side sectional view from viewpoint A-A of the capacitivesensing apparatus 300B in accordance with various embodiments of theinvention. Within FIGS. 3 and 6, the capacitive sensing apparatus 300Bincludes capacitive sensor 200 configured to sense object 303 (e.g., auser's finger, a probe, a stylus, and the like) proximate to thephysical capacitive sensing reference surface 502. It is appreciatedthat the capacitive sensing apparatus 300B can include a plurality ofdielectric materials (e.g., 602 and 604) disposed between the capacitivesensor 200 and the physical capacitive sensing reference surface 502.

The capacitive sensor 200 can be circular in some embodiments to matchthe two-dimensional projection of the physical capacitive sensingreference surface 502, but it can also be some other shape that allowssensing at least within the capacitive sensing reference surface 502.The areas outlined by dielectric materials 602 and 604 can differ fromeach other in the shape or size. The areas outlined by dielectricmaterials 602 and 604 can also be substantially the same or differ fromthe area outlined by the capacitive sensing reference surface 502. Forexample, dielectric materials 602 and 604 can fall within or extendbeyond the area outlined by the capacitive sensing reference surface502. Also, the size or shape of capacitive sensor 200 can extend (asshown) beyond, fall within, or be substantially the same as the areaoutlined capacitive sensing reference surface 502. Note that at leastone of the plurality of dielectric materials (e.g., 602 and 604) canhave a non-uniform thickness. The actual size and shape chosen would inpart be determined by the exact sensing technology and implementation ofcapacitive sensing apparatus 300B. Dielectric materials 602 and 604 areconfigured such that capacitive coupling (or specific capacitance perunit area) between the capacitive sensor 200 and an object, e.g., 303,(not shown) proximate to the physical capacitive sensing referencesurface 502 is substantially constant as the object moves across thephysical capacitive sensing reference surface 502. In this manner,standard sensing circuitry can be utilized in conjunction withcapacitive sensing apparatus 300B without needing any compensationcircuitry or software. It is noted that capacitive sensing apparatus300B can be inexpensive to design and fabricate since it can incorporatea substantially flat or planar capacitive sensor 200.

For example, the capacitive sensing apparatus 300B can include (asshown) the dielectric materials 602 and 604, which are juxtaposed andare different dielectric materials. Therefore, the amount and locationof a first dielectric material (e.g., 602) and the amount and locationof a second dielectric material (e.g., 604) together affect capacitivecoupling. Since at least one of the dielectric materials (e.g., 602) ofcapacitive sensing apparatus 300B has varying thickness, at least oneother dielectric material (e.g., 604) also has a varying thickness suchthat its effects can be utilized to offset the varying capacitancecaused by the change in thickness of dielectric material 602. It isnoted that one or more different dielectric materials (e.g., 604) can beutilized to offset the varying capacitive coupling caused by the changein thickness of dielectric material 602.

For a fixed dielectric constant for dielectric material 602, thethickness of dielectric material 604 can be varied so that the netcapacitive coupling (or specific capacitance per unit area) between thecapacitive sensor 200 and an object (e.g., 303) proximate to thephysical (or tangible) capacitive sensing reference surface 502 issubstantially constant as the object moves across the physicalcapacitive sensing reference surface 502. By selecting different valuesfor the shapes and dielectric constants of dielectric materials 602 and604, the capacitive coupling can be actively controlled. In general, thedielectric constant is fixed for a given material. So for a specificmaterial, its thickness is one factor that can be varied to control thecapacitance.

For instance, if dielectric material 602 having vary thickness as shownin FIG. 6 is implemented as a plastic having variable thickness and adielectric constant approximately equal to 4, and the dielectricmaterial 604 when implemented as air has a dielectric constantapproximately equal to 1, dielectric material 604 can be disposed withvarying thickness (as shown) in order to offset the variation incapacitance caused by the vary thickness of dielectric material 602. Forexample, arrow 606 indicates where dielectric material 602 is at itsthinnest while arrow 608 indicates where dielectric material 604 is atits thickest.

It is appreciated that there are a wide variety of ways to modelcapacitive coupling to define the configuration of one or moredielectric materials in accordance with the invention. For example,these models can be used to define the thickness of dielectric material602, dielectric material 604, and/or other materials in a capacitivesensing apparatus such that capacitive coupling (or specific capacitanceper unit area) between capacitive sensor 200 and an object proximate toa physical capacitive sensing reference surface of the capacitivesensing apparatus is substantially constant as the object moves acrossthe physical capacitive sensing reference surface. These models can alsobe of varying levels of accuracy and complexity, from simple idealizedtextbook equations to intricate finite element analyses, and it is wellknown how to derive approximations from fundamental electromagneticfield equations such as Maxwell's Equations. For example, an idealparallel plate capacitor model of two conductive plates separated by onedielectric material means that the resulting capacitive coupling betweenthe two conductive plates is proportional to the dielectric constant ofthe dielectric material and inversely proportional to the thickness ofthe dielectric material.

FIG. 7 illustrates a side sectional view from viewpoint A-A ofcapacitive sensing apparatus 300C wherein each section (e.g., 702, 704or 706) near A-A has approximately the same specific capacitance perunit area, in accordance with various embodiments of the invention.Therefore, when an object 708 (e.g., a probe, a user's finger, a stylus,and the like) contacts the physical or tangible capacitive sensingreference surface 502 of the capacitive sensing apparatus 300C withinsection 706, the capacitive coupling (or specific capacitance per unitarea) between object 708 and capacitive sensor 200 within section 706will be approximately or substantially constant when compared to whenobject 708 alternatively contacts the physical capacitive sensingreference surface 502 within section 702 or 704. As such, the capacitivesensing apparatus 300C has substantially the same sensitivity everywhereon reference surface 502 to a uniform object (e.g., 708) even thoughobject 708 is at different distances from the capacitive sensor 200.Therefore, the sensing signals of the capacitive sensing apparatus 300Care substantially on the same scale, thereby enabling approximately thesame gain to be increased on all the sensing signals received fromcapacitive sensing apparatus 300C.

Note that object 708 can be utilized with any capacitive sensingapparatus (e.g., 300, 300A, 300B, 300C, 300D, 300E, 300F, 1100,1400 and1600) that is mentioned herein.

It accordance with the invention, it is understood that any dielectricmaterials (e.g., 302, 402, 602 and 604) can be implemented in a widevariety of ways. For example, each of dielectric materials 602 and 604can be implemented with, but is not limited to, one or more polymers,one or more plastics, one or more foam materials, one or more gases(e.g., air), and the like. Within the capacitive sensing apparatus 300C,the physical capacitive sensing reference surface 502 can be implementedin any non-flat manner, such that it includes, but is not limited to,any combination of flat, concave, convex, conical, wavy, triangularsaw-toothed, pyramidal, V-shaped, U-shaped, and/or any arbitrarynon-uniformly flat shapes.

Within capacitive sensing apparatus 300, 300A, 300B, 300C and the like,it is appreciated that capacitive sensor 200 can be implemented as oneor more sensing traces or elements and the sensing circuitry orelectronics (e.g., 210) can be located somewhere else. Furthermore, thecapacitive sensor 200 in accordance with various embodiments of theinvention can be implemented such that it is substantially flat orplanar, but is not limited to such. For example, in accordance withvarious embodiments of the invention, the capacitive sensor 200 can beimplemented such that is substantially curved or non-planar, but is notlimited to such.

Within FIGS. 6 and 7, it is understood that the plurality of dielectricmaterials (e.g., 602 and 604) of the capacitive sensing apparatuses 300Band 300C may not be implemented as layers. Instead, within variousembodiments, one dielectric material (e.g., 602) can internally includeone or more regions or sections of another dielectric material (e.g.,604) in order to provide capacitive coupling (or specific capacitanceper unit area) between the capacitive sensor 200 and an object (e.g.,303 or 708) proximate to the physical (i.e. tangible) capacitive sensingreference surface 502 that is substantially constant as the object movesacross the physical capacitive sensing reference surface 502.

FIG. 8 illustrates a side sectional view from viewpoint A-A ofcapacitive sensing apparatus 300D implemented with an additionalmaterial 802 that has a substantially uniform thickness in accordancewith various embodiments of the invention. In other embodiments,material 802 has varying thickness and is configured along withdielectric materials 602 and 604 to achieve uniform capacitive coupling.In many cases, material 802 will also be a dielectric, although material802 may be semi-conductive or conductive in some cases to improvesensing or for electric shielding. Material 802 may also be patterned,such as to achieve the desired aesthetic appeal, tactile feel, orelectrical effects on the sensing or shielding properties of capacitivesensing apparatus 300D. It is appreciated that material 802 can beimplemented as a touch surface material that provides a contact surfacefor an object (e.g., 303 or 708) interfacing with the capacitive sensingapparatus 300D. Material 802 can alternatively be interposed betweendielectric materials 602 and 604, between dielectric material 604 andcapacitive sensor 200 such that it is closer to dielectric material 604instead of dielectric material 602, or anywhere else as long as itresides at least partially between the capacitive sensor 200 and thecapacitive sensing reference surface 502. Material 802 can be disposedagainst the plurality of dielectric materials (e.g., 602 and 604) ofcapacitive sensing apparatus 300D such that there is physical contactbetween material 802 and at least one of the dielectric materials 602and 604. Additional materials can also be included (not shown) inaddition to dielectric materials 602 and 604, and material 802.

Within FIGS. 6 and 7, the physical (tangible) capacitive sensingreference surface 502 in accordance with various embodiment can bedefined as the active area where capacitive coupling (specificcapacitance per unit area) between an object (e.g., 303 or 708) and thecapacitive sensor 200 is substantially constant across capacitivesensing reference surface 502. It is appreciated that the physical (ortangible) capacitive sensing reference surface 502 can be implementedas, but is not limited to, at least part of a touch surface material(e.g., 802 of FIG. 8) or at least part of the top surface of adielectric material (e.g., 602 as shown in FIGS. 6 and 7).

FIG. 9 illustrates a side sectional view from viewpoint A-A ofcapacitive sensing apparatus 300E wherein dielectric material 604 hasbeen implemented in regions defined by dielectric material 602 andcapacitive sensor 200 in accordance with various embodiments of theinvention. It is understood that one or more additional differentdielectric materials can be implemented within capacitive sensingapparatus 300E in a manner similar to dielectric material 602, but isnot limited to such. It is appreciated that by implementing dielectricmaterial 604 as shown in FIG. 9, structural support and stability can beprovided to dielectric material 602 and capacitive sensing apparatus300E by supports 902 when an object (e.g., finger 303) is pressedagainst its physical (i.e., tangible) capacitive sensing referencesurface 502. It is noted that supports 902 can be implemented such thatthey are narrow in comparison to the size of the physical capacitivesensing reference surface 502. In this manner, supports 902 will notsubstantially affect the resulting capacitive coupling between an object(e.g., finger 303, and the like) and capacitive sensor 200 as the objectis moved across capacitive sensing reference surface 502.

FIG. 10 illustrates a side sectional view from viewpoint A-A ofcapacitive sensing apparatus 300F wherein dielectric material 604 hasbeen implemented as elliptical regions and a circular region defined bydielectric material 602 in accordance with various embodiments of theinvention. Note that one or more additional different dielectricmaterials can be implemented within capacitive sensing apparatus 300F ina manner similar to dielectric material 602, but is not limited to such.By implementing dielectric material 604 as shown in FIG. 10, structuralsupport and stability can be provide to dielectric material 602 andcapacitive sensing apparatus 30OF by supports 1002 when an object (e.g.,303 or 708) is pressed against its physical capacitive sensing referencesurface 502. It is understood that supports 1002 can be implemented suchthat they are narrow in comparison to the size of the physicalcapacitive sensing reference surface 502. In this fashion, supports 1002will not substantially affect the resulting capacitive coupling betweenan object (e.g., finger 303, and the like) and capacitive sensor 200 asthe object moves across capacitive sensing reference surface 502.

FIG. 11 is a top view of an exemplary capacitive sensing apparatus 1100that includes a physical (i.e. tangible) capacitive sensing referencesurface 1102 in accordance with various embodiments of the invention.Specifically, the physical capacitive sensing reference surface 1102 canbe incorporate with a casing 1104. Furthermore, the physical capacitivesensing reference surface 1102 can include discrete concave regions anddiscrete convex regions that involve vector linear lines. Note that thephysical capacitive sensing reference surface 1102 can be implementedwith one or more discrete straight or curved lines in any non-uniformshape, but is not limited to such. FIG. 12 is a side sectional view fromviewpoint B-B of the capacitive sensing apparatus 1100 in accordancewith various embodiments of the invention.

Within FIGS. 11 and 12, the capacitive sensing apparatus 1100 includescapacitive sensor 200 configured to sense an object (e.g., finger 303, aprobe, a stylus, and the like) proximate to the physical capacitivesensing reference surface 1102. The capacitive sensing apparatus 1100can include a plurality of dielectric materials (e.g., 602 and 604)disposed between the capacitive sensor 200 and the physical capacitivesensing reference surface 1102. The capacitive sensor 200 can be squarein some embodiments to match the two-dimensional projection of thephysical capacitive sensing reference surface 1102, but it can also besome other shape that allows sensing at least within the capacitivesensing reference surface 1102.

The areas outlined by dielectric materials 602 and 604 can differ fromeach other in the shape or size. The areas outlined by dielectricmaterials 602 and 604 can also be substantially the same or differ fromthe area outlined by the capacitive sensing reference surface. The areasoutlined by dielectric materials 602 and 604 of capacitive sensingapparatus 1100 can also be substantially the same or differ from that ofthe area outlined by the capacitive sensing reference surface 1102. Forexample, dielectric materials 602 and/or 604 can fall within or extendbeyond the area outlined by the capacitive sensing reference surface1102. Also, the size or shape of capacitive sensor 200 can be such thatcapacitive sensor 200 is substantially the same (as shown), extendbeyond, or fall within the area outlined capacitive sensing referencesurface 1102. Thus, the size of capacitive sensor 200 can be smaller orsubstantially the same as the area of capacitive sensing referencesurface 1102. Note that at least one of the plurality of dielectricmaterials (e.g., 602 and 604) can have a non-uniform thickness. Theactual size and shape chosen would in part be determined by the exactsensing technology and implementation of capacitive sensing apparatus1100. Dielectric materials 602 and 604 are configured such thatcapacitive coupling (or specific capacitance per unit area) between thecapacitive sensor 200 and an object (e.g., 303 or 708) proximate to thephysical capacitive sensing reference surface 1102 is substantiallyconstant as the object moves across the physical capacitive sensingreference surface 502.

For example, the capacitive sensing apparatus 1100 can include (asshown) the dielectric materials 602 and 604, which are juxtaposed andare different dielectric materials. As such, the amount and location ofa first dielectric material (e.g., 604) and the amount and location of asecond dielectric material (e.g., 602) together affect capacitivecoupling. Since at least one of the dielectric materials (e.g., 602) ofcapacitive sensing apparatus 1100 has varying thickness, at least oneother dielectric material (e.g., 604) also has a varying thickness suchthat its effects can be utilized to offset the varying capacitancecaused by the change in thickness of dielectric material 602. Note thatone or more different dielectric materials (e.g., 604) can be utilizedto offset the varying capacitive coupling caused by the change inthickness of dielectric material 602.

Within FIG. 12, the capacitive sensing apparatus 1100 can include anoptional on-board circuitry 1202, which enables the functional operationof capacitive sensor 200. Note that the on-board circuitry can belocated in a wide variety of locations associated with capacitivesensing apparatus 1100. Within FIG. 12, the on-board circuitry iscoupled to capacitive sensor 200. It is understood that any capacitivesensing apparatus described herein can be implemented with on-boardcircuitry, such as on-board circuitry 1202.

FIG. 13 is a flow diagram of a method 1300 in accordance with variousembodiments of the invention for forming a capacitive sensor apparatus.Although specific operations are disclosed in method 1300, suchoperations are exemplary. That is, method 1300 may not include all ofthe operations illustrated by the flow diagram in FIG. 13.Alternatively, method 1300 may include various other operations and/orvariations of the operations shown by the flow diagram in FIG. 13.Likewise, the sequence of the operations of method 1300 can be modified.Noted that the operations of method 1300 may include utilizing software,firmware, electronic hardware, fabrication hardware tools, or anycombination thereof.

Specifically, a first dielectric material having varying thickness canbe disposed above a capacitive sensor. Furthermore, a second dielectricmaterial can be disposed adjacent to the first dielectric material. Itis noted that the capacitive coupling (specific capacitance per unitarea) of the capacitive sensor through the first and second dielectricmaterials to an object proximate to a physical capacitive sensingreference surface is approximately constant across the physicalcapacitive sensing reference surface. Moreover, a third dielectricmaterial having substantially uniform thickness can be disposed abovethe second dielectric material. Note that the third dielectric materialcan provide a contact surface for the object to touch.

At operation 1302 of FIG. 13, a first dielectric material (e.g., 604)having varying thickness can be disposed above a capacitive sensor(e.g., 200). It is appreciated that operation 1302 can be implemented ina wide variety of ways. For example, the first dielectric material(e.g., gas, air, polymer, plastic, and the like) having varyingthickness can be disposed at operation 1302 above a capacitive sensor inany manner similar to that described herein, but is not limited to such.

At operation 1304, a second dielectric material (e.g., 602) can bedisposed adjacent to the first dielectric material. Note that thecapacitive coupling (specific capacitance per unit area) of thecapacitive sensor through said first and second dielectric materials toan object (e.g., 708) proximate to a physical capacitive sensingreference surface (e.g., 502) is approximately constant at differentlocations across the physical capacitive sensing reference surface. Itis appreciated that operation 1304 can be implemented in a wide varietyof ways. For example, the second dielectric material can be disposedadjacent to the first dielectric material at operation 1304 in anymanner similar to that described herein, but is not limited to such.

At optional operation 1306 of FIG. 13, a third material (e.g., 502),which could be a dielectric having substantially uniform thickness, canbe disposed above and/or adjacent to the second dielectric material. Itis understood that the third dielectric material can provide a contactsurface for the object to touch. Note that operation 1306 can beimplemented in wide variety of ways. For example, the third material,which could be a dielectric material having substantially uniformthickness, can be disposed at operation 1306 above and/or adjacent tothe second dielectric material in any manner similar to that describedherein, but is not limited to such. At the completion of operation 1306,process 1300 can be exited.

FIG. 14 is a top view of an exemplary capacitive sensing apparatus 1400that includes a physical (i.e. tangible) capacitive sensing referencesurface 1402 in accordance with various embodiments of the invention.Specifically, the physical capacitive sensing reference surface 1402 caninclude discrete concave regions and discrete convex regions thatinvolve vector linear lines. It is noted that the physical capacitivesensing reference surface 1402 can be implemented with one or morediscrete straight or curved lines in any non-uniform shape, but is notlimited to such. FIG. 15 is an exemplary side sectional view fromviewpoint C-C of the capacitive sensing apparatus 1400 in accordancewith various embodiments of the invention.

Within FIGS. 15, dielectric materials 602 and 604 of capacitive sensingapparatus 1400 do not overlap each other beneath the physical (ortangible) capacitive sensing reference surface 1402. The dielectricmaterials 602 and 604 have been implemented such that portions ofdielectric material 602 are thinner than dielectric material 604 withinthe area outlined by capacitive sensing reference surface 1402. Inaccordance with one embodiment, dielectric material 604 can have ahigher dielectric constant than dielectric material 602. Therefore, inorder to achieve uniform capacitive coupling between capacitivereference surface 1402 and capacitive sensor 200, the thickness of thedielectric material 604 can be greater than the thickness of dielectricmaterial 602 within the area outlined by capacitive sensing referencesurface 1402.

As shown by dielectric material 602 of FIG. 15, dielectric materialextends beyond the area outlined by capacitive sensing reference surface1402 and can have varying thickness for aesthetic reasons such as visualappeal, or functional reasons such as visual or tactile feedback or toaddress electrical fringing effects. It is appreciated that byimplementing dielectric materials 602 and 604 as shown in FIG. 15,tactile and visual feedback can be provided to an object (not shown)interacting with the capacitive sensing surface 1402 and will notsubstantially affect the resulting capacitive coupling between theobject and capacitive sensor 200 as the object moves across the physicalcapacitive sensing reference surface 1402.

FIG. 16 is a top view of an exemplary capacitive sensing apparatus 1600that includes a physical (i.e. tangible) capacitive sensing referencesurface 1602 in accordance with various embodiments of the invention.Specifically, the physical capacitive sensing reference surface 1602 caninclude discrete concave regions and discrete convex regions thatinvolve vector linear lines. It is appreciated that the physicalcapacitive sensing reference surface 1602 can be implemented with one ormore discrete straight or curved lines in any non-uniform shape, but isnot limited to such. FIG. 17 is an exemplary side sectional view fromviewpoint D-D of the capacitive sensing apparatus 1600 in accordancewith various embodiments of the invention.

Within FIG. 17, dielectric materials 602 and 604 of capacitive sensingapparatus 1600 do not overlap each other beneath a physical (ortangible) capacitive sensing reference surface 1602. Dielectricmaterials 602 and 604 of capacitive sensing apparatus 1600 have beenimplemented such that some portions of dielectric material 602 arethinner than dielectric material 604 within the area outlined bycapacitive sensing reference surface 1602. Additionally, neitherdielectric material 602 nor dielectric material 604 has varyingthickness within the area outlined by capacitive sensing referencesurface 1602. Within one embodiment, dielectric material 604 can have ahigher dielectric constant than dielectric material 602. Therefore, inorder to achieve uniform capacitive coupling between capacitivereference surface 1602 and capacitive sensor 200, the thickness of thedielectric material 604 can be greater than the thickness of dielectricmaterial 602 within the area outlined by capacitive sensing referencesurface 1602.

It is understood that dielectric material 602 (as shown) of capacitivesensing apparatus 1600 extends beyond the area outlined by capacitivesensing reference surface 1602 and can have varying thickness foraesthetic reasons such as visual appeal, or functional reasons such asvisual or tactile feedback or to address electrical fringing effects. Byimplementing dielectric materials 602 and 604 as shown in FIG. 17,tactile and visual feedback can be provided to an object (not shown)interacting with the capacitive sensing surface 1602 and will notsubstantially affect the resulting capacitive coupling between theobject and capacitive sensor 200 as the object moves across the physicalcapacitive sensing reference surface 1602.

Within FIG. 2, the capacitive sensor 200 can also be implemented as acapacitive touch screen device. For example, substrate 202 of capacitivesensor 200 can be implemented with, but is not limited to, one or moresubstantially transparent materials that are utilized as a substrate fora capacitive touch screen device.

It is noted that if it was not desirable to achieve uniform capacitanceper unit area (or capacitive coupling), but instead a controlledcapacitance per unit area, techniques similar to those described hereincan be utilized in order to produce any desired capacitive per unit areafunction. By using any combination of the methods described herein, itis possible to control the capacitive profile of the reference surfaceto the capacitive sensor.

The foregoing descriptions of specific embodiments in accordance withthe invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The invention can be construed according to the Claims andtheir equivalents.

1. A capacitive sensing apparatus comprising: a capacitive sensorconfigured to sense an object proximate to a physical capacitive sensingreference surface; and a plurality of dielectric materials disposedbetween the capacitive sensor and the physical capacitive sensingreference surface, at least one of said plurality of dielectricmaterials having non-uniform thickness, wherein said plurality ofdielectric materials is configured such that capacitive coupling betweensaid capacitive sensor and said object proximate to said physicalcapacitive sensing reference surface is substantially constant acrosssaid physical capacitive sensing reference surface.
 2. The capacitivesensing apparatus of claim 1, wherein at least one of said plurality ofdielectric materials is comprised of a foam material.
 3. The capacitivesensing apparatus of claim 1, wherein at least one of said plurality ofdielectric materials is comprised of a gas.
 4. The capacitive sensingapparatus of claim 3, wherein said gas comprises air.
 5. The capacitivesensing apparatus of claim 3, wherein at least one of said plurality ofdielectric materials is comprised of a polymer.
 6. The capacitivesensing apparatus of claim 1, wherein said physical capacitive sensingreference surface is not uniformly flat.
 7. The capacitive sensingapparatus of claim 1, wherein said physical capacitive sensing referencesurface is concave.
 8. The capacitive sensing apparatus of claim 1,wherein said physical capacitive sensing reference surface is convex. 9.The capacitive sensing apparatus of claim 1, wherein at least one ofsaid plurality of dielectric materials has a substantially uniformthickness.
 10. The capacitive sensing apparatus of claim 1, furthercomprising a touch surface material disposed against said plurality ofdielectric materials, said touch surface material configured to providea contact surface for said object.
 11. A capacitive sensing apparatuscomprising: a two-dimensional capacitive sensor configured to sense anobject proximate to a tangible capacitive sensing reference surface; anda plurality of layers of dielectric material disposed between saidtwo-dimensional capacitive sensor and said tangible capacitive sensingreference surface, at least one of said plurality of layers ofdielectric material having varying thickness, wherein said plurality oflayers of capacitive material is configured such that the specificcapacitance per unit area between said two-dimensional capacitive sensorand said conductive object proximate to said tangible capacitive sensingreference surface remains approximately constant across said tangiblecapacitive sensing reference surface.
 12. The capacitive sensingapparatus of claim 11, wherein at least one of said plurality layers ofdielectric material is comprised of a gas.
 13. The capacitive sensingapparatus of claim 12, wherein said gas comprises air.
 14. Thecapacitive sensing apparatus of claim 11, wherein at least one of saidplurality layers of dielectric material is comprised of a polymer. 15.The capacitive sensing apparatus of claim 11, wherein said tangiblecapacitive sensing reference surface is not uniformly flat.
 16. Thecapacitive sensing apparatus of claim 11, wherein said tangiblecapacitive sensing reference surface is concave.
 17. The capacitivesensing apparatus of claim 11, wherein said tangible capacitive sensingreference surface is convex.
 18. A method comprising: disposing a firstdielectric material having varying thickness above a capacitive sensor;and disposing a second dielectric material adjacent to said firstdielectric material; wherein capacitive coupling of said capacitivesensor through said first and second dielectric materials to an objectproximate to a physical capacitive sensing reference surface isapproximately constant across said physical capacitive sensing referencesurface.
 19. The method of claim 18, wherein said first dielectricmaterial comprises a gas.
 20. The method of claim 18, wherein saidsecond dielectric material comprises a polymer.
 21. The method of claim18, further comprising: disposing a third dielectric material havingsubstantially uniform thickness above said second dielectric material,said third dielectric material provides a contact surface for saidobject.
 22. The method of claim 18, wherein said physical capacitivesensing reference surface is not uniformly flat.